Watford defender Joel Ekstrand will leave at the end of his contract after four years at Vicarage Road.
The 27-year-old, capped twice by Sweden, has not appeared for the Hornets since suffering a cruciate knee ligament injury in March last year.
In total, he has made 100 appearances for Watford since joining from Udinese, initially on loan.
Meanwhile, Watford have extended the contract of 19-year-old striker Alex Jakubiak until next summer.
But under-21 players George Byers, Josh Doherty, Matt Hall, Uche Ikpeazu, Jorell Johnson, Mahlondo Martin, Bernard Mensah, Luke Simpson and Alfie Young have all been released.